The airplane was in cruise flight on an instrument flight plan in a light drizzle and icing conditions when a total loss of power occurred. The pilot attempted to restart the engine during the forced landing. He remained in communication with ATC during the emergency descent toward the closest airport. The condition of light was dark night and the pilot reported that he did not break out of the weather until nearly reaching the ground. The landing area was rough uneven open prairie. The airplane was damaged during the landing. Post accident examination of the powerplant revealed water in the fuel system in the delivery line between the engine driven fuel pump to the fuel control valve. Additionally, water was found in the intake manifold. The water was drained and the engine was test run without incident. When asked by the FAA, the pilot did not know about the published fuel tank summing procedure relative to trapped water in the bottom of the cells.